The present invention relates to connector systems for spirally wound corrugated pipe used in ducting, and in particular to an improved system for attaching conventional connector elements to the end of a corrugated pipe.
Spirally wound corrugated pipe has become used with increasing frequency in ducting for heating, ventilation and air conditioning (often called the HVAC industry). Such pipe is relatively easy to fabricate and is therefore reasonably inexpensive. In addition, because the pipe is spirally wound and corrugated, it is somewhat flexible, and thus readily installed in a variety of ducting applications.
The advantages of using spirally wound corrugated pipe for ducting are somewhat counterbalanced by the problems involved in obtaining air tight connections between pipe sections. Male and female connector elements are typically installed at the ends of the pipe, which mate together to form a relatively air tight seal. The problem arises in the attachment of the connector elements themselves to the ends of the corrugated pipe sections. Spirally wound corrugated pipe inherently has a rippled configuration at its ends, rendering it difficult to form an air tight seal with the connector element.
Air tight seals in ducting used in the HVAC industry are of paramount concern at the present time because the increasing cost of energy supplies makes it mandatory that such ducting be highly efficient. Any gaps in the seals result in a leakage of the ducted material, requiring more energy input to achieve the desired heating or cooling goals.
It is the present practice in the industry to apply a mastic material between the interior of the end of the corrugated pipe section and the connector element. The mastic fills in the spaces between the connector element and the end of the corrugated pipe section, and also acts as an adhesive to bind the connector element to the pipe. If necessary, staples or self-penetrating rivets are also used to fasten the connector element to the pipe.
The mastic is typically applied by hand, and when corrugated pipe is mass produced, human error inevitably results in uneven application of the mastic. The mastic thus fails to completely fill all of the spaces between the pipe and the connector element, leavings gaps in the seal. In addition, when the pipes are installed, forces are exerted on the connector element relative to the pipe which cause the mastic seal to fail. As a result, conventional application of mastic is generally inefficient in providing an effective seal between the connector element and the pipe.
In conventional connecting systems as described above, the seal can also be broken by denting the connector between the staples or rivets binding the connector element to the pipe. Also, the staples or rivets tear holes in the material, themselves breaking the seal, and provide structural weak points in the pipe system. Because of such problems, the attachment of connector elements to the pipe sections is often the weak point of a duct constructed from spirally wound corrugated material, and is responsible for much of the loss of ducted material.